Field of the Invention and Related Art Statement
The present invention relates to a switch for detecting an erroneous erase protection fin provided on a tape casette such as a video tape cassette and an audio tape cassette.
FIG. 1 is a schematic cross sectional view illustrating the construction of a switch for detecting the existence of the erroneous erase protection fin of tape cassette. The switch comprises a stationary contact strip 1, a movable contact strip 2, both made of a resilient metal, and a main body 3 made of electrically insulating synthetic resin. The switch further includes a first actuation member 4 which is secured to the main body 3 rotatably about a shaft 5, and a second actuation member 7 secured to a free end of movable contact strip 2. The second actuation member 7 is arranged within a space 6 formed in the first actuation member 4. It should be noted that the second actuation member 7 has a substantially triangular cross section and its apex portion is projected beyond the first actuation member 4. A reference numeral 8 denotes a stopper for restricting the rotation of the first and second actuation members 4 and 7 in the clockwise direction, and a reference numeral 9 represents a stopper for preventing the counter-clockwise rotation of the second actuation member 7.
As shown in FIG. 1, the known switch is consisting of the five parts, i.e. stationary contact strip 1, movable contact strip 2, main body 3, first actuation member 4 and second actuation member 7. Therefore, the cost for preparing the parts is liable to be increased and the number of assembling steps becomes large. Further, the force of restitution of the switch is generated only by the resilient force of metal strips 1 and 2, so that the strips are liable to be fatigued and the durability of the switch is short.